IPCC forecasts 9 meter sea-level rise if temperatures meet 2C threshold

Alok Jha in the Guardian (UK): Global sea levels could rise by up to 9m in the next few hundred years, even if the world manages to stabilise average temperatures to 2C above pre-industrial levels, according to a new study. In this scenario, hundreds of millions of people around the world would be affected as low low-lying coastal areas became inundated. New Orleans would be lost to the sea, much of southern Florida and Bangladesh and most of the Netherlands.

The 2C figure is significant because this is level of warming that is likely to be adopted as the threshold to be avoided by the UN climate negotiations in Copenhagen – although small islands states and developing nations have argued that 1.5C would be a more appropriate target.

Nine metres of sea level rise is higher than anything predicted so far because the new study takes into account the potential that the Greenland and west Antarctic ice sheets start to melt as the Earth warms. …"Everybody's known that the IPCC's last numbers were underestimates because they didn't include all the factors that can accelerate ice sheet melting," said Robert Kopp of Princeton University, who led the latest study. "If the future models are limited, you want to look at other approaches to get at the question of sea-level rise one approach is to turn to the past record of sea-level rise."

…His results, published in the journal Nature, showed that sea levels around the world during the last interglacial were between 6.6m and 9m higher than today. "During this period when temperatures were 2-3C above pre-industrial levels, global sea level looks like it was very likely at least 6.6m higher than today, which implies significant melting of the Greenland and west Antarctic ice sheets."….

High tide, view from Boston Lodge towards Porthmadog at high tide. Shot by Dewi for the Geograph project, under the Creative Commons Attribution ShareAlike 2.0 License